1. Field of the Invention
The present invention relates to a keyboard control apparatus wherein an external ten-key pad is connectable to a keyboard body for use in a personal computer or the like.
2. Description of the Related Art
In general, a personal computer has a keyboard, i.e., a data input apparatus, and a display apparatus, i.e., a data output apparatus, which are formed integrally as one piece. The keyboard has various character keys necessary to data input. Recently, however, in a type of personal computer, exclusive numeric keys (ten keys) are not provided and character keys can also be used as numeric keys in order to make the apparatus compact.
The personal computer of this type has overlay keys, which are used as letter keys in a normal state and as numeric keys in a special state (a Numeric Lock State, abbreviated as an NL state). The keyboard apparatus is set in the NL state by operating an NL key. The overlay keys are thus used as letter keys and numeric keys; however, when the two states are frequently switched, the key input efficiency is greatly reduced.
To overcome this drawback, in a type of keyboard apparatus, an external ten-key pad is detachably connected to the keyboard body. When the external ten-key pad is connected to the keyboard body, numbers are input through the external ten-key pad, instead of overlay keys. The external ten-key pad has an NL key as described above, and the keys thereof can be used as, for example, cursor keys in a normal state and as numeric keys in an NL state by operating the NL key.
However, if the NL key of the external ten-key pad is operated to set an NL state so that the ten keys function as numeric keys, the overlay keys in the keyboard body also function as numeric keys, not the normal letter keys. Hence, to use the overlay keys as the normal letter keys, a key operation for resetting the NL state is required.
For example, after the NL key is depressed to set a mode to use the keys of the ten-key pad as numeric keys, if the user wishes to input Roman letters by using overlay keys of the keyboard body, the NL key should be depressed again to release the set mode. The reverse is also conceivable. Thus, the user cannot use the keys of the ten-key pad as numeric keys and the overlay keys of the keyboard body as Roman letter keys, without changing the mode (without operating the NL key).